A headlamp is a lamp attached to the front of a vehicle to illuminate the road ahead of the subject vehicle. World-wide, vehicles have used both sealed beam headlamps and composite headlamps. Sealed beam headlamps are replaceable light bulbs that are typically not enclosed inside headlamp assemblies, while composite headlamps are lamp assemblies with replaceable bulbs that are either enclosed entirely inside or extend outside the headlamp assemblies.
Popular among modern vehicles is a headlamp design using an “H4” halogen light bulb. The H4 bulb as first introduced in Europe includes low beam and high beam filaments in a single bulb, and thus provides the capability to generate both low and high beams from a single bulb. In 1991, a “9003/HB2” bulb that is similar to the H4 bulb, but with stricter limits on bulb filament placement variance and lower allowable light output, was certified for use on vehicles sold in North America.
It may be desirable to seal headlamps using H4 and 9003/HB2 light bulbs from moisture in order to maintain effectiveness and reliability of such headlamps. Sealed headlamp assemblies may be especially useful in off road vehicles that may need to traverse a body of water.